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An explanation on why leaves change colors during the fall.

It’s the spring rains. It’s the warm weather. It’s the long and pleasant "Indian summer." There are a myriad of explanations for the spectacle of leaf color change, but only one is correct.

The fact is, leaves change at the same time each year regardless of the weather. Responding to the longer nights of fall, trees start to slow production of chlorophyll, the pigment responsible for making leaves green and photosynthesis possible, towards the end of August (in the Northern hemisphere).

As chlorophyll vanishes from the plant’s tissues underlying pigments (the reds, yellows, oranges we all look out for) become visible. Things like hot, sunny days combined with chilly nights cause chlorophyll production to wind down rapidly, setting up a vivid, high impact foliage display. Other factors matter too: Drought during the growing season can stress trees out to the point of early leaf drop, and frost, wind and rain can knock leaves right off the trees before they have a chance to dazzle!

So now you know. And next time somebody offers you their opinion on the subject, you be the authority.